volume scatter in blender giving me a dark screen with some crazy amounts of fireflies
There's a circle called circle.001 that you've parented to your lamp object (called Sphere). This circle obstructs your spot light. It won't cause any problem in the Viewport because you've disabled its visibility, but you've enabled it for Renders. So delete this object or disable its visibility for renders.

Also:


Reset the Compositor.
Don't use the Volume Scatter for the whole world, as you explain it looks like you can't use any other light than Spots if it's assigned to the whole world. Instead, create a cube that encompass your scene and give it the Volume Scatter node.